1. Field of the Invention
The present invention relates to a transfer device configured to transfer an article in a stacker crane or a station of an automated transport system.
2. Description of the Related Art
The stacker crane includes the transfer device configured to transfer an article to and from a shelf disposed in an automatic warehouse. In addition, the station of the automated transport system is provided with the transfer device configured to transfer an article to and from a carrier.
As structures of the transfer device, there are a slide fork system in which the article is picked up and transferred by a fork, a suction system in which the article is sucked, held, and transferred, a pickup belt system in which the article is moved to slide and is transferred by a pickup belt, a clamp system in which the article is pinched and held at its both sides and is transferred, and a hook system in which an end of the article is engaged with a hook disposed on a tip of a slide arm so that the article is pushed or pulled and is transferred when the slide arm moves forward and backward.
For instance, there is proposed a transfer device provided with a hook supported in a rotatable manner on a tip of the slide arm (for example, see WO2011/158422).
In WO2011/158422, the hook disposed on the tip of the slide arm rotates with respect to the slide arm and hence can move between an action position contacting with the end of the article and a retract position not contacting with the article.
In an operation of transferring the article from the transfer device to the shelf, the transfer device sets the hook in the action position so as to contact with the end position of the article, and moves the slide arm forward toward the shelf so as to push the article to the shelf.
If the hook in the action position is moved at high speed so as to contact with the end position of the article, damage to the article may be caused. Therefore, an optical sensor is disposed adjacent to a position of the slide arm at which the hook is attached, and the arm is moved at low speed until the optical sensor detects the end position of the article.
In the transfer device described above, because the slide arm is moved at low speed until the hook reaches the contact position, there is a problem that the transfer process takes time.